1. Field of the Invention
The present invention relates to a control apparatus for a hybrid vehicle which is mounted in a hybrid vehicle propulsion driven by jointly using an internal-combustion engine and a motor, and wherein the driving force from at least one of the internal-combustion engine and the motor is transmitted to the driving wheels.
Priority is claimed on Japanese Patent Application No. 2003-192315, filed Jul. 4, 2003, and No. 2003-403211, filed Dec. 2, 2003, the contents of which are incorporated herein by reference.
2. Description of Related Art
Conventionally, for example, in a hybrid vehicle which comprises an internal-combustion engine and a motor as a power source and which transmits the driving force from at least one of the internal-combustion engine and the motor to the driving wheels for traveling, a control apparatus for a hybrid vehicle has been well known which sets an engine torque required by the internal-combustion engine and a motor torque required by the motor according to the operating state of the vehicle.
In such a control apparatus for a hybrid vehicle, for example a control apparatus comprising a constant speed drive unit which drives a vehicle to travel so that the speed of the vehicle (vehicle speed) detected by a vehicle speed sensor follows a target vehicle speed which is a target value of the vehicle speed, has been known. Regarding this constant speed drive unit, the arrangement is such that, if a speed difference is generated between the vehicle speed detected and the target speed, a torque output from the internal-combustion engine and the motor is increased or decreased so as to counteract this speed difference (for example, Japanese Patent Application Unexamined Publication No. Hei 9-207622).
Incidentally, in a hybrid vehicle according to an example of the above conventional technique, for example, in the case where this comprises a variable cylinder internal-combustion engine capable of switching between an all cylinders operation which operates all cylinders and a partial cylinders deactivation operation which operates with some cylinders deactivated (cylinders deactivation operation) as an internal-combustion engine having high fuel consumption efficiency, and this is set in order to switch the all cylinders operation and the cylinders deactivation operation according to the operating state of the vehicle, then in a state where the vehicle is driven to travel so that the detected vehicle speed becomes the target vehicle speed, by simply increasing and decreasing only the torque from the internal-combustion engine and the motor so as to counteract the speed difference between the detected vehicle speed and the target vehicle speed, there is a likelihood that hunting which frequently switches between the all cylinders operation and the cylinders deactivation operation, occurs so that occupants in the vehicle may feel discomfort with respect to travelling behavior.
Moreover, in the control apparatus for a hybrid vehicle comprising such a variable cylinder internal-combustion engine, it is desired to improve the fuel consumption efficiency by enlarging the region which continues the cylinders deactivation operation with respect to, for example an amount of a vehicle state such as the accelerator pedal opening or the vehicle speed.